Dual-comb Spectroscopy of Ammonia Formation in Non-thermal Plasmas

Abstract

Plasma-activated chemical transformations promise the efficient synthesis of salient chemical products. However, the reaction pathways that lead to desirable products are often unknown, and key quantum-state-resolved information regarding the involved molecular species is lacking. Here we use quantum cascade laser dual-comb spectroscopy (QCL-DCS) to probe plasma-activated NH${}_3$ generation with rotational and vibrational state resolution, quantifying state-specific number densities via broadband spectral analysis. The measurements reveal unique translational, rotational and vibrational temperatures for NH${}_3$ products, indicative of a highly reactive, non-thermal environment. Ultimately, we postulate on the energy transfer mechanisms that explain trends in temperatures and number densities observed for NH${}_3$ generated in low-pressure nitrogen-hydrogen (N${}_2$-H${}_2$) plasmas.

References in corpus (6)

• Mid-Infrared Frequency Comb Fourier Transform Spectrometer
• ExoMol molecular line lists XXXV: a rotation-vibration line list for hot ammonia
• Time-resolved mid-infrared dual-comb spectroscopy
• A mid-infrared dual-comb spectrometer in step-sweep mode for high-resolution molecular spectroscopy
• The Rotationally Resolved Infrared Spectrum of TiO and Its Isotopologues
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Cited by in corpus (3)

• Precision spectroscopy of non-thermal molecular plasmas using mid-infrared optical frequency comb Fourier transform spectroscopy
• An air-spaced virtually imaged phased array with 94 MHz resolution for precision spectroscopy
• Formation of HNC and HCN isomers in molecular plasmas revealed by frequency comb and quantum cascade laser spectroscopy